Materials-handling system using autonomous transfer and transport vehicles

ABSTRACT

Methods and apparatus for selecting and combining items in an outbound container through the use of autonomous vehicles, each of which includes means for automatically loading and unloading a payload, to perform both transfer and transport functions in moving containers of items within a workspace via a network of roadways. Under computer control, said autonomous vehicles transfer and transport case containers of item units between incoming receiving stations, intermediate storage locations, and outgoing order-assembly stations where entire containers or individual item units are combined in the outbound container.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Non-Provisional PatentApplication Ser. No. 14/336,829 (now U.S. Pat. No. 9,802,759) filed July21, 2014 which is a continuation of U.S. Non-Provisional PatentApplication Ser. No. 12/563,940 (now U.S. Pat. No. 8,784,034) filed Sep.21, 2009, which is a continuation of U.S. Non-Provisional PatentApplication Ser. No. 10/928,289 (now U.S. Pat. No. 7,591,630), filedAug. 28, 2004, which claims priority from and the benefit of U.S.Provisional Patent Application No. 60/498,688, filed on Aug. 29, 2003,the disclosures of which are incorporated by reference herein in theirentireties.

FIELD OF THE INVENTION

The present invention relates to materials-handling systems and methodsin general, and more specifically to the systems and methods used toselectively pick cases and individual items of merchandise to fulfillorders within retail distribution systems.

BACKGROUND OF THE INVENTION

Retail distribution systems handle merchandise at three basic levels ofaggregation. The first and most granular level is the individual itemunit as packaged for sale to consumers. The second level is the “case”,the container that is filled with item units at the factory, sealed, andthen unsealed either at the store when the items are placed onto shelvesor at an order-fulfillment center where items are to be picked to fillcustomer orders. The third level of aggregation is the pallet, ontowhich multiple cases are stacked for bulk shipping, typically by truck.

By far the most pervasive materials-handling process within anyretailer's distribution system is the selective retrieval (“picking”) ofmerchandise from inventory-either cases or individual item units-to fillorders. Yet, despite a steadily increasing level of automation ofvarious materials-handling processes, order-picking remains a mostlymanual and labor-intensive process, generally using some variant of therelatively inefficient “man-to-goods model”.

In high-volume retail channels, the standard ordering unit forstore-level replenishment is the case. Case-picking to fill store orders(or “order selection”, as in is usually called) occurs in retaildistribution centers (“DCs”). Merchandise arrives at the DC frommanufacturers or intermediate suppliers on pallets, each pallettypically containing cases of a single product. The task of the DC is toship to the stores pallets containing a specified number of cases ofmany different products. The primary method used to transfer cases fromincoming pallets to outgoing pallets is a manual process that haschanged little over many decades: single-product pallets are placed atpicking locations arranged in opposing rows separated by aisle spaces,and human operators (“selectors”) travel on motorized vehicles throughthose aisles, building mixed pallets as they go. On board each vehicleare one or more (typically two) pallets, and the job of the selector isto drive the vehicle to a series of single-product pallets and place aspecified number of cases of each product on the specified outboundpallets. There have been attempts to use machines to automate caseselection, but none has enjoyed significant commercial success to date,and manual case-selection is used in the vast majority of retaildistribution centers in operation today.

Picking of individual item-units occurs at various points in retaildistribution. For example, DCs that supply stores whose physical sizeand sales volumes are too small for case-quantity replenishment mustship individual item units. Types of stores that are usually replenishedin less-than-case-quantity include convenience, drug, and specialtygoods. In addition, there is an ever-increasing demand for item-levelpicking to fill orders that are delivered directly to end-users orconsumers, driven largely by the growth in “e-commerce”, i.e. electronicorders placed from personal computers via the Internet. A. variety of“man-to-goods” methods are used to perform item-level picking. Inapplications where the picking volume is low or the product assortmentis limited, the model is very similar to that used in case-levelorder-selection described above (or by shoppers in a self-servicestore), with pickers taking containers to item locations to make thepicks. In applications with higher volume and wider product assortment,“zone” picking is more typical, with each picker stationed in adesignated area, or zone, and responsible for picking all ordered itemsin that area and placing them into containers (e.g., boxes or totes)that move through the zone on conveyors.

Depending on the application and configuration of the order-fulfillmentprocess, pickers in a typical “man-to-goods” process spend only 15% to30% of their work time actually picking the items and placing themeither on a pallet or in a container. The rest of their time is spenttraveling to the picking locations, ensuring that the target pick is theright item, ensuring the right number of items have been picked, or justwaiting to perform the next transaction. A number of technologies, suchas barcode scanning, voice direction, and pick-to-light have beendeveloped that improve accuracy and improve productivity of non-traveltasks, but the only way to achieve dramatic improvements in laborefficiency is to use a “goods-to-man picking” model in which the goodsto be picked flow to stationary workstations. There have been efforts tocreate goods-to-man item-picking models, most notably through the use ofcarousels and automated storage-and-retrieval cranes, but thesesolutions are typically very expensive and have not been widely adopted.

Of course, by far the most prevalent form of item-picking in retail isthat performed by customers shopping in self-service stores—indeed thevery term “self-service” refers specifically to the process of customerspicking their own orders. There have also been attempts to create a newretail operating model-an automated full-service store-by automatingthis item-picking process. This operating model would have numerousadvantages over the self-service model, as it would simultaneouslyenable much more efficient and effective operations by the retailer andprovide a much more enjoyable and time-efficient shopping experience tothe customer. Some examples of attempts to create this retail operatingmodel include U.S. Pat, Nos. 3,746,130 and 5,890,136 and 5,595,263 and5,933,814 and 5,595,264 and 5,186,281. Unfortunately, none of theseattempts to automate order-fulfillment fulfillment in a retail store hasbeen successful, primarily because a material-handling system has neverexisted that can satisfy the very challenging requirements of thisapplication effectively and affordably.

The objective of the present invention is to provide, for the firsttime, a materials-handling system that allows a high degree ofautomation in the picking of orders at both case-level and item-level,and to automate item-level order picking so effectively that it can beused for real-time order-picking in an automated full-service retailstore.

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description which follows, frequent reference will bemade to the attached drawings, in which:

FIG. 1a , FIG. 1b , and FIG. 1c are top, side, and front views,respectively, of the preferred embodiment of the autonomous transfer andtransport vehicle.

FIG. 2a and FIG. 2b are top and side views, respectively, of an exampleof a carrier tray used in the preferred embodiment.

FIG. 3 shows a side view of the operation of one of the transfer armsaccording to the preferred embodiment of the invention.

FIGS. 4a through 4c show a side view of the sequence of transferring apayload from storage rack onto payload bay according to the preferredembodiment of the autonomous transfer and transport vehicle.

FIG. 5a and FIG. 5b show top and side views, respectively, of theautonomous transfer and transport vehicle with a payload onboard,according to the preferred embodiment of the invention.

FIG. 6 is a topological block diagram of the computer and electronic andelectrical subassemblies of the preferred embodiment of the autonomoustransfer and transport vehicle.

FIG. 7 a top view of one level of the storage structure according to thepreferred embodiment.

FIG. 8 is a partial side view of a storage structure according to thepreferred embodiment.

FIG. 9 is a cross-sectional view of a storage structure according to thepreferred embodiment.

FIG. 10 is a simplified floor plan of an order-picking facility usingthe present invention.

FIG. 11 is a simplified floor plan of an automated full-service retailstore using the present invention.

DETAILED DESCRIPTION Overview

In the preferred embodiment of the present invention, amaterials-handling system designed to pick orders uses autonomousvehicles to handle single cases of merchandise and perform the functionsof both. (1) transferring cases into and out of storage locations (e.g.,a rack) and (2) transporting the cases within the work facility. In mostprior-art systems these two functions are typically performed byseparate subsystems, such as an automated storage-and-removal systemcombined with conveyors. In the present invention, each autonomousvehicle is equipped with two transfer-arm assemblies that together movea single-case payload laterally onto and off of its payload bay, andwith propulsion and guidance mechanisms that enable the vehicle to carryits payload from location to location within the workspace. Combiningboth transfer and transport functions within a single subsystem greatlysimplifies the overall design and operation of the system, therebyreducing costs, increasing reliability, and providing design flexibilityin addressing application-specific system requirements.

The approach solves order picking problem by enabling a “goods-to-man”picking model that is far more labor efficient than the conventional“man-to-goods” model, and much less expensive and more effective thanprevious solutions. Incoming cases of merchandise are depalletized,transported individually into holding storage by the transfer/transportvehicles, and then selectively retrieved and transported by those samevehicles to order-assembly workstations, either pallet-building stationsor item-pick-and-pack stations. If the workstations are manual, labor isused much more productively because all of the time is spent is pickingand placing. Moreover, this model makes it possible eventually toreplace the human operator altogether with a robotic picker orpallet-building machine in a totally automated “goods-to-robot” model.

While each vehicle is designed to handle only single cases, a key aspectof the present invention is “massively parallel” operation: a givensystem will use many of these vehicles to achieve the necessary level oftotal system throughput, all operating independently of each other. Forexample, if a single vehicle can perform an average of 50case-transactions per hour, a system with 200 vehicles would have atheoretical throughput capacity of 10,000 case-transactions per hour,though in actual practice total system throughput degrades somewhat asadditional vehicles are added due to collision-avoidance and congestiondelays.

The use of track-guidance of the vehicles is optional but highlyadvantageous in order to maximize speed of travel with the simplestpossible vehicle design. Track-guidance allows safe travel at high speedby mechanically controlling the path of vehicular motion without complexguidance-control and navigational systems. High-speed travel isimportant to maximizing throughput capacity, since the throughput ofeach vehicle is a function of how fast it can travel from one point toanother, and simplicity of vehicle design is an important factor inminimizing system cost and maximizing reliability.

Track-guidance can take a variety of forms, however, and in thisapplication the best by far is a slotted “guideway”, i.e. a roadway witha guide-slot in the center into which extends a guide pin attached tothe vehicle. In order for vehicles to have random access to multiplelocations within a facility, a key element of the preferred embodimentis a network of guideways interconnected by branching points where thevehicles can change guideways. With slot-guidance, the wheels of thevehicle can simply roll over the slot, so branching can be achieved witha purely passive guideway (i.e. no active switches), and extremelysimple steering means on the vehicle that controls which of twoconjoined slots the guide-pin enters.

For the sake of brevity and in keeping with George Lucas' alphanumericnaming convention for robots, the Track-guided Transfer and TransportVehicle of the preferred embodiment is called “T3V”.

A multi-level storage structure holds the cases of merchandise that arethe picking stock available to fill orders. Each level of this structurehas multiple picking aisles consisting of opposing storage racksseparated by T3V guideways. The guideways are interconnected so thatT3Vs have random access to the cases of merchandise. T3Vs are able toelevate themselves to upper levels of the storage structure by means oframps, which are a highly advantageous alternative to the use ofmechanical lifts that are more expensive and create bottlenecks andadditional point of potential failure.

Another optional but very beneficial element of the preferred embodimentof the present invention is the use of a “carrier tray” to contain thecases of merchandise so that T3Vs manipulate the carrier trays insteadof the cases themselves. The carrier tray serves two important purposes.First, it creates a standard mechanical interface to thepayload-transfer mechanism on the T3V, isolating it from the widevariations in sizes, shapes, and materials of the cases being handled.This results in a transfer mechanism that is much simpler, lessexpensive, and more reliable in operation than one which must be able tomanipulate cases directly. The second advantage of the carrier tray isthe containment of any spillage or leakage of item contents in the case.This benefit is especially important giver the difficulty of cleaning upthe messes in the storage structure that would result from uncontainedspills and leaks, and the consequent impact on operations.

T3Vs enable a novel and highly efficient operating model for a retail DCin which the picking-stock is first depalletized and the individualcases are inserted into carrier trays, picked up by T3Vs and transportedinto the storage structure. Cases are then selectively retrieved by T3Vsand transported to pallet-building workstations, offloaded by T3Vs,removed from the carrier trays, and placed onto the mixed pallets foreventual delivery to stores. It is or will soon be possible for all ofthe processes on both sides of T3V activity to be performed by robots orother machines, so that the operation of the entire DC can be completelyautomated.

A very similar operating model can be used for item-level picking in anorder-fulfillment center or small-store distribution center. Cases aredepalletized and then have their tops removed to expose the individualitem units for picking. These open cases are then inserted into carriertrays, picked up by T3Vs and transported into the storage structure.Cases are then selectively retrieved by T3Vs and transported topick-and-pack workstations where individual item units are removed fromtheir cases and placed into containers (totes, boxes, bags, etc.) fordelivery to the end user. Cases are then returned to storage unlessempty. At the current time, the actual picking of the item is believedto be beyond the capabilities of affordable robots and must be performedby humans, though at maximum labor efficiency.

The T3V is such an effective solution to the problem of automatingitem-picking that it also for the first time makes practicable real-timeorder fulfillment in the automated retail store. In the preferredembodiment of this operating model, the store is basically an item-levelorder-fulfillment facility combined with a shopping section in whichproducts for sale are displayed for customers to evaluate. Rather thancollecting items for checkout, customers order items via a shoppingterminal to be picked by the T3V system.

Design Detail

The preferred embodiment of the T3V (100) is depicted in FIG. 1a (topview), FIG. 1b (side view), and FIG. 1c (front view). The vehicle has achassis frame (101), to which are attached the following major elementsof the vehicle:

-   -   (a) four wheels, two of which are drive wheels (102, 103) and        the other two of which are free turning (104, 105);    -   (b) two drive motors (106, 107) that propel the vehicle by        directly driving each of the two drive wheels (102, 103), and        also provides braking by reversing thrust electronically;    -   (c) a guide-pin assembly (108) at the front of the vehicle that        engages the slot (109) in the guideway to control direction of        vehicular movement;    -   (d) a payload bay (110) that holds cases in carrier trays;    -   (e) two transfer arms (111) that physically pull carrier trays        onto the payload bay (110) and pushes them off;    -   (f) an electronics module (112) containing an embedded control        computer and related interface circuitry, including a wireless        local-area network interface by which the embedded computer        communicates with a system master computer;    -   (g) sensors that provide information to the control computer,        especially about the external environment, such for reading        location markers or aligning the transfer arms with a target        carrier tray in preparation for a payload transfer;    -   (h) a rechargeable battery and related power-conditioning and        distribution circuitry (113), along with connection to external        power.

In the preferred embodiment of the T3V, the drive wheels (102, 103) areat the front of the vehicle along with the guide-pin (108), and twodrive motors (106, 107) are used, one for each drive wheel. While asingle-motor design is certainly feasible, the use of two direct drivemotors has the advantage of mechanical simplicity. For example, there isno need for a drive transmission and differential, nor is a mechanicalsteering system needed since a lateral steering force can be created byturning the drive wheels at different speeds. The use of brushless-DCdrive motors, either single or dual, also eliminates the need formechanical brakes since the direction of force applied to the motor'soutput drive shaft is reversed by reversing the polarity of theelectrical current supplied to the motor, so the motor can be used bothfor propulsion and for braking depending on polarity of current flow.Elimination of these mechanical components also increases systemreliability since brushless-DC drive motors typically have extremely lowfailure rates.

In the preferred embodiment, then, each rear wheel (104, 105) is simplybolted to the chassis (101) through a hub bearing (114) that allows thewheel to turn freely. At the front of the vehicle, it is the two drivemotors (106, 107) that are attached directly to the chassis (101), andeach wheel (102, 103) is attached to the rotating output drive shaft(115) of one of the motors. A problem often encountered with adirect-drive electric motor is the lack of torque at low RPM normallyprovided by the mechanical advantage of a conventional transmissionsystem. This problem is solved in the preferred embodiment by the use ofa drive motor based on the teachings in U.S. Pat. No. 5,067,932, whichcan apply maximum torque to the drive shaft at any speed.

As stated earlier, slot-guidance of the T3V is optional but is used inthe preferred embodiment to enable high vehicular speeds without thecost and design complexity that would be required by unconstrainedself-guidance and—navigation. The key objectives in the design of theslot-guideway and guide-pin assembly are to minimize mechanical stressand frictional wear that will tend to result from high-speed travel. Inthe preferred embodiment shown in FIG. 1b and FIG. 1c , the guidewayconsists of a slot (109), or gap, in the center of the roadway (129),below which is a channel formed by opposing vertical sidewalls (118) oneach side of the slot (109) extending down from the roadway (129). Theguide-pin assembly (108) consists of a guide-pin shaft (116) that isattached at the top to the chassis (101) and extends down into the slotguideway (109), and a pin-tip sub-assembly (117) attached to the end ofthe shaft (116) that actually engages the guideway mechanically bymaking contact with a vertical sidewall (118) extending down fromunderneath the roadway (129) surface. The pin-tip assembly (117)consists of a bracket (119) that is bolted to the end of the guide-pinshaft (116) and holds two contact wheels (120), one on each side of theguideway, which spin horizontally when the wheel (120) comes intocontact the vertical sidewall (118) as the vehicle is moving so as tominimize friction between the guide-pin assembly and the guideway thatwould otherwise result in significant wear and tear at high vehiclespeeds. Thus, when a contact wheel (120) makes contact with the sidewall(118), frictional energy is converted to rotational energy through thespinning of the wheel. The materials used for both the contact wheel(120) and the sidewall (118) should have very low friction coefficientsand be wear-resistant. Of the two, the sidewall material should be theharder and more wear-resistant so that wear and tear will primarilyoccur in the contact wheels, which are readily replaceable, rather thanthe sidewalls, which are not. It should also be noted that the guide-pinassembly (108) should preferably be positioned in the center of a lineconnecting the hubs of the two drive wheels (102, 103), due to the useof ramps, so that the pin-tip assembly (117). will always be at the samevertical elevation as the drive wheels.

If T3Vs were required only to travel on a single closed-loop guidewaylike a typical toy slot-car racer, no additional directional controlwould be needed other than the interaction of the guide-pin assembly(108) in the guideway slot (109). However, since the order-pickingsolution absolutely requires T3Vs to have random access to as manystorage locations as possible, the T3Vs must be able to change guidewaysin the course of navigating to a selected location. This capability isprovided by a network of interconnected guideways featuring forks wheretwo guideways connect, and by providing the T3V with the capability ofselecting which of the two guideways to take when moving through a fork.U.S. Pat. No. 5,218,909 describes one method for providing thisswitching capability in a slot-car racer by moving the guide-pinvertically to either pass over (in the raised position) or engage (inthe dropped position) a sub-surface diverting element in the track.While this method could certainly be used in an embodiment of thepresent invention, a simpler and more reliable approach is used in thepreferred embodiment which takes advantage of the steering effect of aforce differential between the two drive wheels.

A fork in the guideway is formed when a first guideway is conjoined witha second intersecting guideway. As depicted in FIG. 1a , for example, afork (121) is formed when a first guideway slot (109) is joined by asecond guideway slot (122) that runs perpendicular to the first. In thepreferred embodiment, the segment (123) of the second slot (122) thatmerges with the first slot (109) is an arc, or curve, that allows asmooth turn in the transition from the first guideway slot (109) to thesecond (122). It is always the case at a fork that one side of the firstslot (109) is contiguous only with itself, i.e. the corresponding sideof the continuation of the same slot beyond the fork, while the otherside of the first slot (109) is contiguous only with the correspondingside of the second slot (122). Where the second slot (122) isintersecting from the left (from the point of view of the T3V facingforward), as shown in FIG. 1a for example, the right side of the firstslot (109) is contiguous to itself, while the left side of the firstslot (109) is contiguous with the left side of the second slot (122),joining it at the point (124) where the arced segment (123) of thesecond slot (122) merges with the first slot (109). Where the secondslot intersects from the right, the relative sides are reversed.

This feature makes it possible for the T3V (100) to select whichguideway to take at a fork by applying a lateral force to the guide-pinassembly (108) as it moves through the fork (121) to keep the pin-tipassembly (117) in contact with the sidewall (118) contiguous to theselected slot. In the preferred embodiment, this lateral force isgenerated by means of a differential in the forces acting upon the twodrive wheels (102, 103), as is explained more fully below. There are, ofcourse, other ways to create this lateral force, such as a mechanicalmeans for physically displacing a movable guide-pin, similar to themechanism used in U.S. Pat. No. 5,928,058 for causing a toy slot-carracer to shift lanes, or by using a conventional steering mechanism thatturns wheels to change direction.

To further understand how the T3V selects between two guideways at afork, consider what happens when the T3V (100) in FIG. 1a moves throughthe fork (121). When the guide-pin is approximately at the point (124)of contiguity between the two slots (109, 122), the drive motors (106,107) produce a differential in forces acting upon the drive wheels (102,103), for example by applying a braking force to one wheel whileapplying power to the other, which results in a lateral force on theguide-pin in the direction toward the lesser-powered wheel, pressing thepin-tip assembly (117) against the sidewall (118) on that side of theslot. If the T3V is to go straight at the fork, i.e. remain on the firstguideway, the drive motor (106) on the right side of the vehicle brakesits drive wheel (102), while the drive motor (107) on the left side ofthe vehicle holds constant or increases the power it is applying to itsdrive wheel (103). The pin-tip assembly (117) is pressed against theright sidewall (118) as the T3V moves through the fork (121), so thatthe guide-pin assembly (108) remains engaged in the first slot (109) andthe T3V continues on the same guideway. Once the guide-pin has movedpast the point (125) that marks the end of the fork (121) and thecontinuation of the first slot (109), power is once again applied by theright-side drive motor (106) to the right drive wheel (102) to equalizethe forces acting upon the two drive wheels and continue moving the T3Vin a straight line.

On the other hand, if the T3V (100) is to turn left at the fork (121),i.e. transfer to the second guideway, the opposite maneuver isperformed. As the guide-pin assembly (108) moves past the point (124) ofcontiguity between the two slots (109, 122), the left-side drive motor(107) applies a braking force to its wheel (103), while the right-sidedrive motor (106) holds constant or increases the power applied to itsdrive wheel (102). The pin-tip assembly (117) is then presses againstthe left sidewall (118) of the first slot (109) and follows the curve ofthe sidewall into the second slot (122) and the T3V will begin makingthe left-hand turn. Once the guide-pin assembly (108) is fully insertedinto the second slot (122), the braking force on the left-side drivewheel (103) can be released, but because the T3V is now in the processof making a left turn, the inside and outside wheels must still turn atdifferent speeds. The inside (left) drive wheel (103) is allowed to turnfreely, with no power applied, while power is still applied to theoutside (right) drive wheel (102). When the guide-pin reaches the end ofthe curved segment (123) and the beginning of the straightaway, theleft-side drive motor (107) resumes powering its drive wheel with equalforce to that of the right-side drive motor (106), so that the wheelsnow turn at the same speed and propel the T3V in a straight line. (Notethat whenever the T3V is going through a turn, the drive motor on theoutside wheel applies power but the drive motor on the inside eitherlets its wheel turn freely or, when entering a turn at a fork, applies abraking force.)

In the preferred embodiment of the T3V, all of the space between thefront and rear wheels is used for the payload bay (110) which holds acarrier tray being transported by the T3V. The floor of the payload bay(110) has passive rollers (126) to minimize resistance to the lateralmovement of carrier trays during the transfer process. Also mounted tothe floor of the payload bay are two tracks (127) that runlongitudinally from front to back, onto which are movably attached thetwo transfer arms (111), by means of which the T3V transfers payloadsfrom a base platform onto its payload bay and from the payload bay to abase platform. (For purposes of this description, the term “baseplatform” can refer to any horizontal support structure, such as ashelf-like storage rack, a conveyor, a lift, etc.) There are manypossible designs of an operable payload-transfer mechanism, such asthose taught in U.S. Pat. No. 5,380,139. A key design factor, of course,is whether the transfer mechanism must manipulate cases of merchandisedirectly, or, as recommended in the preferred embodiment, it onlymanipulates a container which holds the case of merchandise, calledherein a carrier tray. In the case of the former, a vacuum suctiondevice or mechanical gripper might be used, but the task becomessignificantly simpler with the use of the carrier tray. In the preferredembodiment of the T3V, the payload-transfer mechanism is implemented astwo telescoping transfer-arm assemblies (111) which simultaneouslyextend to the side of the T3V to transfer payloads (carrier trayscontaining cases) on and off the payload bay (110).

An example of a carrier tray (200) is shown in FIG. 2a (top view) andFIG. 2b (side view). It is relatively shallow tray, preferably made of aplastic material, with side walls (201) that are tapered slightly sothat empty trays can be nested for storage, and features that are usedby the transfer mechanism to manipulate the tray. In the preferredembodiment, these manipulating features are notches (202) in the rim ofthe tray, one notch at the top of each end of the four sidewalls (201),or eight notches in total, so that the carrier tray can be manipulatedin any orientation relative to the transfer arms (111).

Details of a transfer arm (111) are further illustrated in FIG. 3, asviewed from the front of the vehicle. Each transfer-arm assembly (111)consists of two nested telescoping members, an outer member (301) andinner member (302), which are slidably attached to a frame (303), whichis in turn movably mounted on tracks (127) on the floor of the payloadbay (110) to align properly with a target carrier tray. At each end ofeach outer telescoping member is finger tab assembly (306), whichconsists of a finger tab (304) and an actuator (305) that can rotate thefinger tab (304) ninety degrees to either of two positions: a vertical(passive) position and a horizontal (active) position. The finger tab(304) remains in the vertical position except when it is involved in aninteraction with a carrier tray (200), as in a transfer into or off ofthe payload bay (110). For this purpose it is placed next to a notch(202) in a carrier tray (200) and rotated into the horizontal positionin the direction of the carrier tray (200), actually entering the notch(202) to create an interference with the carrier tray. When thetelescoping members (301, 302) then move laterally in either direction,the finger tab (304) encounters the vertical wall of the notch (202), sothat continued motion of the telescoping members (301, 302) moves thecarrier tray. The telescoping members (301, 302) can extend in bothdirections, right and left, so that the transfer arms (111) can transfera carrier tray to/from either side of the vehicle. Motors andtransmission means such as pulleys or gears (not shown) effect both thelateral movement of the telescoping members (301, 302) and. thelongitudinal movement of the frame (303) in the tracks (127) on thefloor of the payload bay (110).

The operation of the transfer mechanism to transfer a payload is furtherillustrated in FIGS. 4a through 4c . The T3V begins the transfersequence by positioning itself next to the target carrier tray (200)containing the case payload (401) resting on a base platform (402), asdepicted in FIG. 4a , and independently moving both transfer-armassemblies longitudinally to align with the edges of the target tray.Then, as illustrated in FIG. 4b , the two telescoping members (301, 302)of each transfer-arm assembly (111) are extended to the point at whichthe forward finger tab (304) on each arm is aligned with the rearmostnotch (202) on the carrier tray (200), and the finger tab (304) isrotated downward by the actuator (305) into the notch (202). Thetelescoping members (301, 302) are then retracted back towards the T3V,causing the finger tab (304) on each arm to pull the target carrier tray(200) and case payload (401) in the same direction until, as shown inFIG. 4c , the payload is fully onboard and resting on the rollers on thepayload-bay (110) floor. The transfer from the payload bay (110) onto abase platform (402) occurs in the exact reverse sequence: the T3Vpositions itself in front of the empty space where the carrier tray isto be placed, adjusting the longitudinal position of the carrier tray asnecessary (FIG. 4c ), extends the telescoping members of both transferarms with the active finger tabs still engaged in the notches, therebypushing the carrier tray from the payload bay completely onto the baseplatform (FIG. 4b ). The finger tabs are then rotated upward into thepassive vertical position, and the telescoping members are retractedback to their normal nested position, leaving the carrier tray on thebase platform (FIG. 4a ).

After a T3V has performed its transfer function to pull a payload ontoits payload bay, it holds the payload in place while it performs itstransport function of conveying the payload to wherever the case ofmerchandise needs to be taken. FIG. 5a and FIG. 5b show top and sideviews of the T3V with a payload onboard. The active finger tabs (304)remain engaged in their notches to prevent lateral movement of thecarrier tray during T3V movement, and the transfer arms (111) themselvesprevent longitudinal movement of the payload. By moving along thelongitudinal track (127), the transfer arms (111) can also be used toadjust the position of the carrier tray on the payload bay. If necessaryor desirable in an application, it is possible to increase the number offinger tabs used to engage a carrier tray, and/or incorporate otherlocking mechanisms, in order to increase the security of the hold of thepayload on the T3V.

In the preferred embodiment of the invention, the T3V is an electricallypowered vehicle with a number of onboard electric motors and actuators,and includes a variety of electronic components used for control,sensing, and communication. FIG. 6 is a block diagram of the majorelectrical and electronic components of the T3V. The primary of these isthe embedded control computer that manages all operation of theautonomous vehicle. This is a conventional microcomputer with a CPU,memory, software stored in memory (firmware), and a number ofinput/output ports. The control computer governs the operation of thedrive motors (106, 107) and the motors and actuators in the transferarms (111) by means of control electronics, and uses input from onboardsensors to control the interaction of the T3V with surroundingenvironment.

Location sensors are critical to enabling the T3V to determine itslocation with the work facility at any moment in time. In the preferredembodiment, the location sensors (128) are optical readers (withintegrated light emitters) mounted on the bracket (119) of the pin-tipsubassembly (117), one on each side, facing up toward the underside ofthe roadway (129) surface, where they can read location-encoded opticalindicia placed on that underside surface. Continuous strips of opticalindicia are installed along the entire guideway, one placed on each sideof the slot at a point (130) on the underside surface, facing down to beread by the optical reader that is facing up, where they will be wellprotected from dirt or other contamination that might interfere withreadability. The strips have barcodes at intervals along the way, withadditional interval markers between the barcodes. As the T3V moves alongthe guideway, the pin-tip assembly (117) passes underneath theoptically-encoded strip and the optical readers (128) decode thebarcodes and sense the optical interval markers between barcodes,inputting this data to the control computer. The barcoded data cancontain location information directly or contain arbitrary values thatare linked to a location map in a database. The optically-encodedlocation indicia can be used not only for purely navigational purposes,but also as operational aids to the control computer. For example, thefirmware in the embedded control computer can use these indicia toidentify the points within a fork where the various actions of the drivemotors are required as described earlier.

Also essential are the alignment sensors that make possible the“hand-eye” coordination of the precise movements of the transfermechanism in performing a transfer operation. Indeed, in the preferredembodiment, this analogy is rather literal, as the alignment sensors aresimple miniature cameras (also with integrated light emitters). Twocameras are collocated with the finger-tab assembly (306) on each end ofeach transfer arm. One of the cameras in each pair faces in thedirection of movement of the transfer arm and is used to align the armwith the edge of the target carrier tray, while the second camera facedtowards the center of the T3V payload bay and is used to align thefinger tab with the target notch in a target carrier tray. Theoperational performance of these sensors is also enhanced (and thedesign itself simplified) by placing reflective markers on the carriertrays themselves.

Additional sensors that can prove advantageous are those that providestatus information to the embedded control computer about T3Vcomponents, such as drive-wheel RPM and pressure-sensor feedback fromthe guide-pin assemby, and object-proximity detectors for fail-safecollision-avoidance.

In the preferred embodiment of the invention, the embedded controlcomputer communicates with a system master-control computer by means ofan onboard radio-frequency local-area network (RF LAN) interface, suchas one based on IEEE 802.11b standards.

Operation of the electric motors, actuators, and all of the electronicsin the T3V obviously requires a source of electric power, as well aspower-conditioning and distribution circuitry. There are basically twochoices: electrifying the guideway and equipping the T3V with contactpick-ups, along the principles used to power electric trains, or userechargeable batteries, which is the simplest approach and for thatreason the one used in the referred embodiment. Of course, these choicesare not mutually exclusive. For example, it may be advantageous to userechargeable batteries to avoid the expense and reliability issuesinvolved with electrifying all guideways throughout the facility, but toelectrify the guideways around workstations, where T3Vs must spendsignificant amounts of time moving slowly and queuing for transaction.In this way it would be possible for T3Vs to recharge their batterieswithout having to reduce duty cycle by taking themselves offline to goto a recharging station.

An order-picking system will typically require a storage facility inwhich to place picking stock, i.e. the merchandise to be used in fillingorders. In the present invention, this facility is a storage structure,typically having multiple levels, which essentially provides T3Vs randomaccess to storage locations where carrier trays can be placed. FIG. 7depicts a top view of a single level (700) of a storage structureaccording to the preferred embodiment of the invention, showing severalT3Vs at work. Aisles (701) are formed by opposing rows of storage racks(702) separated by guideways within which T3Vs operate. A T3V travels upa guideway ramp (704) to reach the level (except for the ground-floorlevel, of course), travels down an entry guideway (705) to the specifiedaisle and turns through a fork (121) to enter the aisle, travels to thespecified storage location (706), executes the specified transferfunction either by pushing a carrier tray from its payload bay onto thestorage rack (702) or pulling a carrier tray from the storage rack ontoits payload bay, continues down the remaining length of the aisle, andturns onto an exit guideway (707) that leads down the exit ramp (708)back to ground level. To simplify traffic control and minimizeopportunity for collisions, all travel is one-way. FIG. 8 shows a sideview of a storage structure (800) with six levels (700), including theground level, and the configuration of ramps (704) leading to each level(700).

In order to maximize storage density within the facility, the intervalbetween two levels should be only high enough to allow clearance of theT3Vs operating on the lower level, as is drawn in FIG. 8. In that case,however, ramps to consecutive levels will not provide sufficientclearance for T3Vs to transition the change in pitch without hitting thenext higher ramp if they are stacked directly above each other, asillustrated by the T3V (801) beginning the climb to level 3. Thesolution to this problem is to divide the set of ramps into two stacks,each consisting of ramps to alternate levels (one to odd-numbered levelsand the other to even-numbered levels), and placing these two stacksside-by-side, as shown in FIG. 8, or one in front of the other.

One very practical problem that must be considered in design of ahigh-density storage rack, in which the interval between levels may onlybe 18 inches or less, is how to gain access to a T3V that hasmalfunctioned within the interior of a lower level, as the spaces wouldbe too tight for even small people to service the failed T3V. Thesolution to this problem is illustrated in a cross-sectional view of astorage structure (800) according to the preferred embodiment shown inFIG. 9, with six levels (700). In this design, guideways are made up ofpairs of panels (901) that are attached rotatably, as with a hinge, tothe support frame (902) of the storage structure (800) such that theycan be opened up from above, as shown. Furthermore, all levels haveidentical layouts and are aligned vertically so that each aisle on alower level is directly beneath the corresponding aisles on all higherlevels. With this design, then, access to a failed T3V is gained fromabove by rotating open the guideway panels directly above the failed T3Vone after another from the top level down. For example, as depicted inFIG. 11, suppose that the T3V (903) on the third level (904) of thesix-level storage structure has failed in the middle of a transfer. Theproblem would be corrected by opening the guideway panels on the toplevel (sixth level) immediately above the failed T3V, then thecorresponding guideway panels on the next two levels down to expose theproblem T3V (903) so that corrective action can be taken through manualintervention. Once the problem has been corrected, the guideway panels(901) are returned to normal horizontal position in the reverse orderand normal operations are resumed. During this entire procedure,operations must be suspended only within the one affected aisle on eachof the affected levels. As shown in FIG. 9, T3Vs can continue to operateon the same aisle on lower levels, and also on all other aisles on alllevels within the structure.

In some applications, the merchandise to be stored in the storagestructure will include frozen and refrigerated products that requirelower-than-ambient temperature control. To meet that requirement, thestorage structure can be designed to permit sections to be lined withthermally insulating panels that isolate the air mass with thosesections, thereby permitting efficient cooling of that air, with aircurtains or plastic-strip curtains that permit T3Vs to enter and exitaisles within the refrigerated or frozen sections while preventingsignificant loss of cooled air.

As has been noted, in the preferred embodiment of the present invention,the operation of all T3Vs within a work facility is controlled by asystem master computer, which communicates with individual T3Vs via anRF-LAN. The system master computer performs a number of executiveprocesses within a given application, but the two processes thatdirectly affect the T3Vs are task scheduling and traffic control. Thetask-scheduling function takes as input a stream of tasks that need tobe performed by T3Vs within a rolling window of time into the future,and the fleet of operational T3Vs available to perform those tasks, andproduces a rolling schedule specifying which tasks are to be performedby which T3Vs at what times. A simple example of a scheduled task for agiven T3V might be: go to location A to arrive by time X, transfercarrier tray from base platform on right side of vehicle onto payloadbay, take payload to location B to arrive by time Y, and transfer ontobase platform to left of vehicle. (The task-scheduling software isresponsible for managing the entire fleet of operational T3Vs, so thatany time there is idle T3V capacity, i.e., fewer T3Vs needed to performtasks than are available, the task-scheduler will create a “park andwait for further instructions” task.)

The scheduled tasks that are output by the task-scheduling process onthe system master computer are then input to the traffic-controlprocess, which performs a function very similar to what air-trafficcontrollers do in the system of air travel. The traffic-control functiondecomposes each scheduled task into a series of very specific routinginstructions, or “vectors”, that ensure that the task is accomplishedsuccessfully while avoiding collision with any other T3V. For example,the traffic-control process would instruct the T3V, starting from aspecified location at a specified time, to accelerate at a specifiedrate to a specified speed, maintain that speed for a specified time inorder to arrive at a second specified location at a second specifiedtime, decelerate at a specified rate to a lower specified speed, executea turn at a specified fork to change to a different guideway, etc. Theseinstructions are transmitted to the T3V over the RF-LAN, along with atime-synchronization signal to ensure the T3V operates on the sametime-base as the system master computer. At this point, the T3V assumesresponsibility for executing those routing instructions precisely asgiven. The T3V also reports back in to the traffic-control process aseach routing instruction is performed to provide a feedback loop, ineffect permitting the traffic-control process to create a virtual “radarscreen” of all T3V activity and ensure that operations are going asplanned. Of course, when unexpected events occur and operations don't goas planned, both of these processes must have robust problem-solvinglogic to try to stabilize operations, which would include raising alertsand/or alarms to human supervisory staff to take action.

Note that this recommended software architecture is only one possibleapproach to solving the general management-and-control problem inherentin a large-scale parallel system such as this. It has the advantage ofrunning the most complex software processes in the system mastercomputer, which can be a very powerful server-class machine, rather thanin the T3Vs embedded control computer, thereby minimizing the amount ofcomputational power—and thus the cost—required in the T3V itself. Thoseskilled in the art, however, will recognize that other methods andembodiments are readily possible.

Applications of T3V

As mentioned earlier, the T3V system solves the general problem ofautomating order-picking by making possible a highly efficientgoods-to-man operating model in the short term and a goods-to-robotmodel in the longer term. To show how this solution works in practice,FIG. 10 shows a simplified example of a floor plan of an order-pickingfacility using the present invention, illustrating both a retaildistribution center where orders are picked at case level and anitem-level order fulfillment center.

In a retail DC using the present invention, the order picking processbegins at depalletization workstations (1001) with the removal of casesfrom single-product pallets received from suppliers, either immediatelyupon arrival or after having been placed into temporary storage. At eachworkstation, cases are taken off the pallet either manually orpreferably by completely automated depalletizing machines that arecommercially available at present, and sent down a conveyor. Inaccordance with the preferred embodiment of the present invention, whichuses carrier trays to hold the cases, the next step within eachworkstation is the insertion of the singulated cases into the carriertrays, either by manual or preferably automated means. The output ofeach depalletizing workstation, then, is a stream of carrier trays, eachholding a single case of merchandise. As instructed by the system mastercomputer, more specifically by the task-scheduling and traffic-controlprocesses running on that computer, T3Vs then come to a pick-up point atthe workstation, transfer the carrier trays one at a time onto theirpayload bays, and (typically) transport each case into the storagestructure (800) to a specified empty storage location and transfer thecarrier tray onto the storage rack. Then, again as instructed by thesystem master-control computer as required for the building of outboundmixed pallets, T3Vs go to specified locations in the storage structure(800), transfer specified carrier trays at those locations from thestorage racks onto their payload bay, transport these carrier trays tospecified order-assembly workstations (1002) where mixed pallets arebuilt. At each order-assembly workstation (1002), T3Vs transfer theircarrier trays onto a conveyor at a drop-off point, and the cases arethen removed from the carrier trays and placed on an outbound mixedpallet, either by manual or preferably by automated means. The carriertray is then recycled for re-use. (It should be noted that, instead oftransporting a case of merchandise into the storage structure to beretrieved on a subsequent transaction, a T3V can “cross-dock” it, i.e.transport it directly to a pallet-building workstation to be usedimmediately, thereby effectively saving most of an entire round-triptransaction. Because this is the most efficient use of T3V resources,system master-control computer generally tries to scheduledepalletization and palletization activities to maximize opportunitiesto cross-dock.)

In an item-level order-fulfillment center using the present invention,the order picking process is very similar to the case-level processdescribed above. In fact, there are only two significant differences: anadditional step at the depalletization station is the removal of thecase top to expose individual item units for picking, and cases arereturned to the storage structure after each item pick unless empty.Thus, referring again to FIG. 10, the order picking process begins atdepalletization workstations (1001) with the removal of cases fromsingle-product pallets received from suppliers, either immediately uponarrival or after having been placed into temporary storage. As eachworkstation, the singulated cases immediately have their tops removed.Automated top-removal machines are commercially available that removethe top from a cardboard case while it travels down a conveyor by firstpassing is through a light-curtain to measure the case's dimensions andthen passing it through cutting blades precisely positioned based on themeasured dimensions to cut the case material along all four sides of thebox, after which a suction mechanism adheres to the top and pulls itaway. With their tops off to expose individual item units for picking,the cases are then inserted into carrier trays, either by manual orpreferably automated means. The output of each depalletizing workstation(1001), then, is a stream of carrier trays, each holding a singleopen-top case of merchandise. As instructed by the system mastercomputer, more specifically by the task-scheduling and traffic-controlprocesses running on that computer, T3Vs then come to a pick-up point atthe depalletization station (1001), transfer the carrier trays one at atime onto their payload bays, and then transport each case into thestorage structure (800) to specified empty storage location and transferthe carrier tray onto the storage rack. Then, again as instructed by thesystem master-control computer as required for the picking of items tofill orders, T3Vs go to specified locations in the storage structure,transfer specified carrier trays at those locations from the storageracks onto their payload bay, and transport these carrier trays tospecified order-assembly workstations (1002). In an item-levelorder-fulfillment center, order assembly involves a pick-and-packprocess in which a specified number of items are removed from the caseand placed in an outbound shipping container such as a box or tote. Forthe simplest possible process with the minimum number of transfers, thecase payload remains on the T3V through the pick transaction. If thereare any items remaining in the case after the pick is complete the T3Vis instructed to return the carrier tray back to a specified location inthe storage structure (usually but not necessarily the originallocation), otherwise the T3V is instructed to drop off the carrier trayat a recycling station where the empty case is discarded and the carriertray recycled for re-use. The simplest and lowest cost process forhandling outbound shipping containers once filled will typically be toplace them in carrier trays and transport them by T3V to final shippingstations, since this uses the same system and only requires a smallincremental increase in total number of T3Vs, but conventional conveyorscan also be used.

At the time of this writing, there are very few commercially availablerobots or special-purpose machines that can be used to automate theorder-assembly process at the case level, and none at the item level,though this is likely due to the lack of demand and that situation canbe expected to change if the present invention becomes widely used.However, even if the order-assembly process is performed manually, thepresent invention results in a very large increase in productivity—onthe order of four or five times—compared to conventional man-to-goodsmethods today. Indeed, with the present invention it is possible for asingle human operator to fulfill item-level orders at a rate of 1,000item-picks per person-hour, so that only five operators can pick as manyitems—5,000 or so per hour—as might be purchased in a typical retailstore at peak volume.

The present invention, then, makes possible a new operating model for aretail store far different than the conventional self-service store: theautomated full-service store, in which customers shop by ordering itemswith an electronic shopping terminal instead of collecting them inshopping carts, and the orders are then picked in real time anddelivered to pick-up bays for the customers to pick up as they leave thestore.

FIG. 11 a simplified floor plan illustrative of an automatedfull-service store based on the present invention. The store is dividedinto two major sections, a shopping section (1101) where customersselect the items they wish to purchase, and an order-fulfillment section(1102). An order pick-up area (110) is located outside the store.

The order fulfillment section (1102) is essentially a smaller-scaleversion of the item-level order-fulfillment center described above.Cases of merchandise arrive at the store on mixed-product palletsshipped from a distribution center and are processed at a depalletizingstation (1001) in exactly the same way as described above: cases aretransferred from the pallet to a conveyor, have their tops removed, areinserted into carrier trays, picked up by T3Vs, transported into thestorage structure (800), and transferred onto a storage rack. Asrequired to fill customer orders, T3Vs also retrieve cases containingordered items from the storage structure, transport them toorder-assembly stations (1002) where the ordered number of items areremoved from each case and placed into a shopping bag (or equivalentcontainer), and then ether return the cases to the storage structure(800) or, when empty, drop cases off at a recycling station. In thepreferred embodiment of the automated store, the shopping bags areself-supporting, placed in carrier trays, transported to theorder-assembly stations by T3Vs, and then once filled transported byT3Vs to the pick-up bays.

The shopping section (1101) includes a lobby area (1104) and aproduct-display area (1105). In the lobby (1104), preferably along awall to save floor space, is a bank shopping terminals (1106), and anumber of automated checkout stations (1107).

The shopper goes through the entry way (1109) into the store lobby(1104), picks up a shopping terminal, and then shops in theproduct-display area, where item units are placed on display fixtures(1108) for examination and evaluation only. Typically, there is only onedisplay unit per product, though retailers may add additional displayunits of certain products for promotional emphasis or to reducecontention for high-volume items. The shopper handles display units forinformational purposes in order to make purchase decisions, but thenreturns them to their places on the display fixtures. The actual orderis created by scanning the UPC barcodes printed on display-item packagesand on their shelf labels. (Note that other machine-readable identifierscould be used, such as RFID tags or touch-memory buttons, but UPCbarcodes are used in the preferred embodiment for reasons of simplicityand low cost.)

In the preferred embodiment of the automated store, the shoppingterminal is essentially a mobile battery-powered computer consisting ofa CPU, memory, a wireless network interface (such as 802.11b), a barcodescanner, and a user interface consisting of a screen that displaysinformation to the user, buttons and/or a transparent touch-screenoverlay that accept touch-input from the user. The software on thescanner includes an operating system. (such Linux), a browser (such asOpera), and device drivers. Application-server software running on thesystem master computer produces the information to be displayed on thescreen. The browser on the shopping terminal controls the interactiveexchange of information between the terminal and the application-serversoftware and displays server-provided information on the terminal'sscreen. Stored in the memory of each shopping terminal is a uniqueidentifier used to identify the terminal (and therefore the shopper) tothe application-server software. Two examples of existing commerciallyavailable hand-held devices that could be used as the shopping terminalare the PPT2800 and the PDT7200 from Symbol Technologies, Inc.

When a customer scans a UPC to order an item, the application-serversoftware first checks the on-hand availability of that item. If there isan unreserved unit of the item in the order-fulfillment section, theapplication-server software reserves it for the shopper and transmitsback to the terminal's browser a screen update showing the item'sdescription, its price, and the new order total including the item. Onthe other hand, if there is no unreserved unit of the item in theorder-fulfillment section, the application-server software transmitsback an out-of-stock advisory so the shopper can immediately make analternate selection. At any time during the shopping trip, the customercan cause the terminal to display a list of the customer's order showinga description of each item ordered and its cost, and the total cost ofthe complete order. Typically items can only be added to the list byscanning product UPCs as described above, but the number of units of anyitem already on the list can be easily changed using the touch screeninterface and/or the buttons on the front of the terminal. For example,the customer might scroll up or down the list and select an item, andthen change the order by incrementing or decrementing the number ofordered units for that item. (Also, once an item has been added to theorder list, each subsequent scan of the item's UPC barcode incrementsthe number of units that item in the order, e.g., scanning an item'sbarcode three times is an order for three units of that item.) With eachincrement of the number of units of an item order, the computer followsthe same procedure described above: it checks available stock, reservesan item unit if available, and updates the terminal's screen to show theorder with the additional item unit or an out-of-stock advisory. Witheach decrement of the number of units of an item order, the centralcomputer updates the terminal's screen to reflect the removal of theitem unit, and also removes the “reservation” previously placed on thatitem unit in the picking stock, freeing it to be ordered by anothercustomer. (If the number of units for an item ordered by a customer isreduced to zero, the item description is not removed from the order listbut continues to be displayed with a zero unit count. Decrementing theitem order further will have no effect, but the customer can increasethe item order again through the screen/button interface without havingto physically return to the item's shelf location.)

Once the shopping trip is complete, the shopper proceeds to an availablecheckout station (1107) located in the lobby. Resembling an ATM at abank, each checkout station (1107) is itself a computer with a CPU,memory, network interface (wireless or wired), and an array ofperipheral devices that include a coupon capture device, a cashexchanger, a magnetic card reader, a printer, and a touch-sensitivescreen. Each checkout station also has an identifying barcode locatedprominently on its face, and the customer initiates the checkoutprocedure by scanning this barcode with the shopping terminal, whichactivates the checkout station and deactivates the shopping terminal.After making any last-minute quantity changes, the customer commits thecontents of the order and makes payment using coupons, cash, and/orelectronic funds transfer. By installing an abundance of checkoutmachines, the retailer can effectively eliminate the need for anycustomer to waiting in line at checkout.

In general, the system master computer waits until the customer hascommitted the order before beginning the order-picking process describedabove so that the customer can change the quantity of any ordered itemat any time without cost to the retailer. If a customer changes thequantity of an ordered item after it has been picked, a secondtransaction will be required-either a duplicate pick or a “reverse pick”in which the item is removed from the bag and placed back into the case.Another advantage of waiting until order confirmation is that thesoftware on the system master computer can better optimize thedistribution and combinations of items among multiple bags when thetotal set of items is known. During peak period of demand, however, itmay be necessary to pick parts of some orders prior to finalconfirmation in order to maximize utilization of T3Vs and maintainacceptable service levels.

Once payment is complete, the checkout station (1107) prints out a paperreceipt that includes a barcoded identification number. The screendisplays a message which thanks the customer for shopping at the store,requests return of the shopping terminal, and advises the customer ofthe approximate length of time before the order will be ready forpickup. The customer then returns the terminal to the bank of shoppingterminals, proceeds to his or her car, and drives to the pickup area(1103). At the pickup area (1103), a sign directs the customer to aspecific pick-up bay (1110), where the customer's order will have beendelivered by T3Vs. The barcode on the receipt is scanned for validation,and the order is then released for loading into the customer's car,either by the customer or by a store associate.

CONCLUSION

It is to be understood that the methods and apparatus which have beendescribed above are merely illustrative applications of the principlesof the invention. Numerous modifications may be made by those skilled inthe art without departing from the true spirit and scope of theinvention.

What is claimed is:
 1. A storage and retrieval system comprising: amultilevel storage structure, each level of the multilevel storagestructure including storage locations and branching vehicle supportroadways disposed adjacent the storage locations, the branching vehiclesupport roadways having more than one roadway level so that each roadwaylevel is at a different level of the multilevel storage structure; atleast one autonomous wheeled transport vehicle configured to traversethe branching vehicle support roadways, where the at least oneautonomous wheeled transport vehicle includes a transfer mechanism fortransferring at least one unpalletized shipping case, forming a notpalletized case payload, to and from the at least one autonomous wheeledtransport vehicle, and the branching vehicle support roadways include asubstantially flat non-deterministic road surface configured to allowrotation of the at least one autonomous wheeled transport vehicle on thesubstantially flat non-deterministic road surface for selecting one ofthe branching vehicle support roadways at a branch junction location;and at least one transfer station adjacent to at least one of thebranching vehicle support roadways, the at least one transfer stationand the at least one autonomous wheeled transport vehicle beingconfigured to transfer the not palletized case payload from the at leastone transfer station to the at least one autonomous wheeled transportvehicle; wherein the at least one autonomous wheeled transport vehicleis configured to transfer the not palletized case payload between the atleast one transfer station and the storage locations.
 2. The storage andretrieval system of claim 1, wherein the at least one transfer stationcomprises a source transfer station configured to product containersinto the storage and retrieval system.
 3. The storage and retrievalsystem of claim 1, wherein the at least one transfer station comprises adestination transfer station configured to output product containersfrom the storage and retrieval system.
 4. The storage and retrievalsystem of claim 1, wherein the branching vehicle support roadwayscomprise, at each level, a subnetwork of roadways, wherein eachsubnetwork of roadways is joined to a subnetwork of roadways on avertically adjacent level by an inclined ramp roadway configured totransport the at least one autonomous wheeled transport vehicle betweeneach level of the multilevel storage structure.
 5. The storage andretrieval system of claim 1, wherein the at least one autonomous wheeledtransport vehicle is self propelled by a drive motor coupled to at leastone wheel of the at least one autonomous wheeled transport vehicle. 6.The storage and retrieval system of claim 1, further comprising aprogrammed processor configured to issue commands to the at least oneautonomous wheeled transport vehicle to effect control of the at leastone autonomous wheeled transport vehicle.
 7. The storage and retrievalsystem of claim 1, wherein the at least one autonomous wheeled transportvehicle comprises a steering mechanism responsive to steering commands,issued by a programmed processor of the storage and retrieval system,for effecting control of a direction of travel of the at least oneautonomous wheeled transport vehicle on the branching vehicle supportroadways.
 8. The storage and retrieval system of claim 1, wherein the atleast one autonomous wheeled transport vehicle comprises a positionsensor configured to determine a current position of the at least oneautonomous wheeled transport vehicle within the storage and retrievalsystem.
 9. A method for combining a selection of different products in adistribution facility, said method comprising: providing a storagehaving stacked levels of storage locations, each of said storagelocations being located immediately adjacent to a vehicle supportroadway in a network of roadways with more than one roadway level sothat each roadway level is at a different one of the stacked levels ofstorage locations, at least one roadway of said network of roadwaysincluding a branching location at which the at least one roadway dividesinto different branching roadways which lead to different ones of saidstorage locations; providing a source transfer station connected to oneof said roadways in said network of roadways; providing a destinationorder assembly station connected to one of said roadways in said networkof roadways; providing a plurality of wheeled transport vehicles, eachgiven one of said vehicles being movable from its current location insaid network of roadways to a specified target location in said networkof roadways via a selected one of said branching roadways at eachbranching location that said given one of said vehicles encountersthrough said network of roadways from said current location to saidtarget location and rotating said given one of said vehicles, movingthrough said network of roadways, so as to select the selected one ofsaid branching roadways on encountering at least one of each branchinglocation from said current location to said target location;unpalletizing shipping cases where each of said vehicles furtherincludes a transfer mechanism for transferring at least one unpalletizedshipping case, forming a not palletized case payload, to and from saidvehicle; storing a multiplicity of different products in said storage byrepeatedly: moving a selected vehicle, of the plurality of wheeledtransport vehicles, to said source transfer station, individuallytransferring, with said transfer mechanism on said selected vehicle, thenot palletized case payload of the at least one unpalletized shippingcase that contains a common packaged product, the not palletized casepayload being individually transferred to said selected vehicle at saidsource transfer station, moving said selected vehicle along said networkcarrying said not palletized case payload from said source transferstation to a designated one of said storage locations, and individuallytransferring, with said transfer mechanism on said selected vehicle, thenot palletized case payload of the at least one unpalletized shippingcase from said selected vehicle to said designated storage location; andretrieving and combining a selection of different products stored insaid storage by repeatedly: moving a specified vehicle to a specifiedone of the storage locations, where a given one of said differentproducts is stored, individually transferring, with said transfermechanism on said specified vehicle, an unpalletized shipping casestored at said specified storage location to said specified vehicle toform a not palletized case payload of at least one stored shipping case,moving said specified vehicle along said network of roadways carryingsaid at least one stored shipping case from said specified storagelocation to said destination order assembly station, and transferringthe at least one stored shipping case from said specified vehicle tosaid destination order assembly station.
 10. The method as set forth inclaim 9, wherein the stacked levels of storage locations comprises aplurality of vertically stacked storage levels and wherein each of saidstorage levels comprises multiple storage locations positioned on agiven one of said vertically stacked storage levels immediately adjacentto a substantially level subnetwork of roadways positioned on said givenone of said vertically stacked storage levels.
 11. The method as setforth in claim 10, further including at least one inclined ramp roadwayfor transporting said wheeled transport vehicles from a subnetwork ofroadways on one of said storage levels to a subnetwork of roadways on adifferent one of said storage levels.
 12. The method as set forth inclaim 9, wherein each of said wheeled transport vehicles is selfpropelled by a drive motor mounted on said vehicle and coupled to leastone of its wheels.
 13. The method as set forth in claim 12, wherein saidmotor is responsive to commands from a programmed processor forcontrolling the vehicle's velocity.
 14. The method as set forth in claim9, wherein each of said wheeled transport vehicles includes a steeringmechanism for following a selected one of said branching roadways whenone of said branching locations is encountered in said network ofroadways.
 15. The method as set forth in claim 9, further comprisingdetermining and storing data accessible to a programmed processorindicating the current position of each of said wheeled transportvehicles on said network of roadways.
 16. The method as set forth inclaim 9, wherein each given one of said wheeled transport vehiclesfurther includes a propulsion and guidance mechanism for moving saidgiven one of said vehicles from its current location in said network ofroadways to a specified target location in said network of roadways. 17.An automated product selection system for combining a selection ofdifferent products in a distribution facility comprising: a storagehaving stacked levels of storage locations, each of said storagelocations being located immediately adjacent to a vehicle supportroadway in a network of roadways with more than one roadway level sothat each roadway level is at a different one of the stacked levels ofstorage locations, at least one roadway of said network including abranching location at which the at least one roadway divides intodifferent branching roadways which lead to different ones of saidstorage locations; a source transfer station connected to one of saidroadways in said network of roadways; a destination order assemblystation connected to one of said roadways in said network of roadways;and a plurality of wheeled transport vehicles, each given one of saidvehicles being movable from its current location in said network ofroadways to a specified target location in said network of roadways viaa selected one of said branching roadways at each branching locationthat said given one of said vehicles encounters through said networkfrom said current location to said target location and said given one ofsaid vehicles being configured so as to rotate moving through saidnetwork to select the selected one of said branching roadways onencountering at least one of each branching location from said currentlocation to said target location, where each of said vehicles furtherincludes a transfer mechanism for transferring at least one unpalletizedshipping case, forming a not palletized case payload, to and from saidvehicle; wherein each of said wheeled transport vehicles is configuredto: traverse the network of roadways to said source transfer station,individually transfer, with said transfer mechanism on a selectedvehicle, of the plurality of wheeled transport vehicles, the notpalletized case payload of at least one unpalletized shipping case thatcontains a common packaged product, the not palletized case payloadbeing individually transferred to said selected vehicle at said sourcetransfer station, traverse said network of roadways carrying said notpalletized case payload from said source transfer station to adesignated one of said storage locations, individually transfer, withsaid transfer mechanism on said selected vehicle, the not palletizedcase payload of the at least one unpalletized shipping case from saidselected vehicle to said designated storage location, so that amultiplicity of different products are stored in said storage; andwherein each of said wheeled transport vehicles is further configuredto: traverse the network of roadways to a specified one of the storagelocations, where a given one of said different products is stored,individually transfer, with said transfer mechanism on said specifiedvehicle, an unpalletized shipping case stored at said specified storagelocation to said specified vehicle to form a not palletized case payloadof at least one stored shipping case, traverse along said network ofroadways carrying said at least one stored shipping case from saidspecified storage location to said destination order assembly station,and transfer the at least one stored shipping case from said specifiedvehicle to said destination order assembly station, so that a selectionof different products stored are retrieved and combined.
 18. Theautomated product selection system as set forth in claim 17, wherein thestacked levels of storage locations comprises a plurality of verticallystacked storage levels and wherein each of said storage levels comprisesmultiple storage locations positioned on a given one of said verticallystacked storage levels immediately adjacent to a substantially levelsubnetwork of roadways positioned on said given one of said verticallystacked storage levels.
 19. The automated product selection system asset forth in claim 18, further including at least one inclined ramproadway for transporting said wheeled transport vehicles from asubnetwork of roadways on one of said storage levels to a subnetwork ofroadways on a different one of said storage levels.
 20. The automatedproduct selection system as set forth in claim 17, wherein each of saidwheeled transport vehicles is self propelled by a drive motor mounted onsaid vehicle and coupled to least one of its wheels.
 21. The automatedproduct selection system as set forth in claim 20, wherein said motor isresponsive to commands from a programmed processor for controlling thevehicle's velocity.
 22. The automated product selection system as setforth in claim 17, wherein each of said wheeled transport vehiclesincludes a steering mechanism for following a selected one of saidbranching roadways when one of said branching locations is encounteredin said network of roadways.
 23. The automated product selection systemas set forth in claim 17, further comprising at least one sensorconfigured to determine and effect storage of data accessible to aprogrammed processor indicating the current position of each of saidwheeled transport vehicles on said network of roadways.
 24. Theautomated product selection system as set forth in claim 17, whereineach given one of said wheeled transport vehicles further includes apropulsion and guidance mechanism for moving said given one of saidvehicles from its current location in said network of roadways to aspecified target location in said network of roadways.